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Biology SL > 3.5 Genetic Modification > Flashcards

3.5 Genetic Modification Flashcards

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1
Q

what is PCR?

A

an artificial method of reploicating DNA under laboratory conditions

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2
Q

what does PCR do?

A

amplify large quantities of a specific sequence of DNA from an initial minute sample (each reaction cycle doubles the amount of DNA)

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3
Q

what is he stages of PCR?

A
  1. denaturation - DNA sample is heated to separate it into 2 single strands (95 degrees)
  2. annealing - DNA primers attach to the 3’ end of the target sequence (55 degrees)
  3. elongation - a heat tolerant DNA polymerase (Taq) binds to the primer and copies the strand (72 degrees)
    (this all occurs in thermal cycler)
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4
Q

what is gel electrophoresis?

A

lab techniques used to separate and isolate proteins/ DNA fragments based on size

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5
Q

How does gel electrophoresis work? (3)

A
  • samples placed in a block of gel and electric current is applied which causes the samples to move through the gel
  • smaller samples are less impeded by gel matrix and will move faster
  • samples of different sized to separate as they travel at different speeds
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6
Q

how does DNA separation work in gel electrophoresis? (4)

A
  • DNA may be cut into fragments using restriction endonuclease (different DNA samples produce different fragment lengths)
  • fragments separate because DNA is negatively charged due to presence of phosphate group on each nucleotide
  • DNA samples are placed into an agarose gel and fragment size calculated by comparing against industry standards
  • specific sequences can be identified by incorporating a complementary radiolabelled hybridisation probe, transferring the separated sequences to a membrane and then visualising via autoradiography
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7
Q

how does protein separation work in gel electrophoresis?

A
  • proteins may be folded into a variety of shaped and have positive and negative regions
  • proteins must be treated with anionic detergent (SDS) to linearise and impart a uniform negative charge
  • protein samples placed into polyacrylamide gel and sized compared to industry standards
  • separated proteins transferred to membrane and then target proteins are identified by staining with aa specific monoclonal antibody
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8
Q

what is DNA profiling?

A

technique by which individuals can be identified and compared via DNA profiles

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9
Q

how does DNA profiling work?

A
  • within non-coding regions of an individuals genome there exists satellite DNA made up of short tandem repeats (STR)
  • as individuals will likely have different number of repeats at a given satellite DNA locus, they will generate unique DNA profiles
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10
Q

what is the procedure of DNA profiling? (4)

A
  • DNA sample is collected and amplified using PCR
  • satellite DNA (w/ STR sequences) are cut with specific restriction enzymes to generate fragments
  • fragment length will differ between individuals due to variable length of their STR
  • the fragments are separated using gel electrophoresis and profiles are compared
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11
Q

what is the genes between species called?

A

gene modification

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12
Q

what is the name of the organism created from genetic modification?

A

transgenic

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13
Q

what is the summary of the process of gene transfer?

A
  1. isolation of gene and vector (by PCR)
  2. digestion of gene and vector (by restriction endonuclease)
  3. ligation of gene and vector (by DNA ligase)
  4. selection and expression of trangenic contruct
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14
Q

what is step one of the process of gene transfer?(3)

A
  • DNA isolated from cells via centrifugation (heavier components eg nuclei are separated)
  • gene of interest can be specifically amplified via PCR
  • gene sequences can also be generated from mRNA using reverse transcriptase these DNA sequences lack introns
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15
Q

what is a vector in gene transfer?

A

DNA molecules used as a vehicle to carry the green into a foreign cell

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16
Q

why are bacterial plasmids commonly used as vectors?

A

they are capable of autonomous self-replication and expression

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17
Q

what is step 2 of the process of gene transfer? (2)

A
  • to incorporate a gene of interest into a vector they must be cut with restriction enzymes at specific recognition sites
  • restriction enzymes cleave the sugar-phosphate backbone to generate blunt or sticky ends (complementary overhangs)
18
Q

why will scientists often cleave the vector and gene with 2 sticky ends restriction endonucleases?

A

to ensure the gene is inserted in the correct orientation and prevent the vector from re-annealing without the desired insert

19
Q

what is the step 3 of gene transfer? (4)

A
  • gene of interest is inserted into a plasmid vector that has been cut with restriction endonucleases
  • thick occurs as sticky ens of the gene and vector overlap via complementary base pairings
  • gene and vector are spliced together by DNA ligase to form a recombinant construct
  • DNA ligase joins the vector and gene by fusing their sugar-phosphate backbones with a covalent phosphodiester bond
20
Q

what is the 4th step of gene transfer?

A
  • the recombination construct with the desired gene is introduced into an appropriate host cell
  • process can be achieved in a variety of ways and is called transfection or transformation
  • antibiotic selection is used to identify which cells have successfully incorporated the recombinant construct
  • the plasmid vector contains an antibiotic resistance gene so only transgenic cells will grow in the presence of antibiotics
  • transgenic cells once isolated and purified will begin expressing the desired trait encoded by gene if interest
21
Q

how can GMOs help human health? (2)

A
  • incorporating genes for certin proteins, vitamin of vaccines
  • GM crops can be manufactured that lack allegens or toxins
    (the inclusion or removal of some genes can trigger unexpected adverse health reactions)
22
Q

what are the benefits of GMOs?(7)

A
  • nutritional value can be added
  • crops that lack allergens
  • crops grow in arid conditions for better yield (drought)
  • produce herbicides to kill pests
  • improve agriculture/food supply in poor countries
  • GM crops may have longer shelf lives
  • reduced economic costs and carbon footprint (less land for cleaning and pesticides usage)
23
Q

what are the risks of GMOs? (7)

A
  • new traits could cause adverse health problems
  • removal of traits could have unknown effects
  • crops may limit biodiversity of local environment
  • cross-pollination could lead to superweeds
  • patent restricts farmers form accessing GMO seeds
  • foods with GMO are not labelled
  • different government may have conflicting regulatory standards concerning safe usage
24
Q

what is Bt corn?

A

genetically modified maize that incorporated an insecticide-producing gene
(lethal to certain types of larvae of European corn borer)

25
Q

what concerns have been raised gainst Bt corn?

A

the survival of monarch butterflies
(larva feed on milkweed, wind-born pollination of pollen from Bt corn may dust nearby milkweed)

26
Q

what occurred in the experiment where exposure and survivor rates of monarch butterflies were measured? (3)

A
  • monarch butterflies fed on milkweeds dusted with pollen from Bt corn
  • growth and mortality rates were compared against caterpillars fed on non-dusted leaves
  • caterpillars exposed to Bt pollen were found to have eaten less, grew more slowly and higher mortality rates
27
Q

why did some scientists argue that the experiment lacked validity?

A
  • higher amount of Bt pollen on leaves that would be found naturally
  • larva were restricted in diet
28
Q

what were the results of the second study conducted?

A
  • there was no significant increase in mortality when monarch larva were placed in/near an actual Bt corn field
  • concluded that Bt pollen caused no significant risk to monarch butterfly population
29
Q

what are clones?

A

groups of genetically identical organisms/ group of cells derived from 1 single original parent cell

30
Q

what is required for the cloning of multicellular organisms?

A

stem cells (somatic cell nuclear transfer)

31
Q

what is the process of somatic cell nuclear transfer? (5)

A
  • somatic cells are removed from the adult donor and cultured (these cells are diploid and contain entire genome)
  • an unfertilised egg is removed from a female adult and its haploid nucleus is removed to produce an enucleated egg cell
  • enucleated egg is fused with the nucleus from the adult donor to make a diploid egg cell
  • an electric current is delivered to stimulate the egg to divide and develop into an embryo
  • embryo is implanted into the uterus of a surrogate and will develop into genetic clone of adult donor
32
Q

what are animal cloning methods? (4)

A

binary fission
budding
fragmentation
parthogenesis

33
Q

what is binary fission?

A
  • the parent organism divides equally in 2 and produce 2 genetically identical daughter cells
  • this method is common in bacteria and protists and flatworms
34
Q

what is binary fission? (2)

A
  • the parent organism divides equally in 2 and produce 2 genetically identical daughter cells
  • this method is common in bacteria and protists and flatworms
35
Q

what is budding? (2)

A
  • cells split off the parent organism generating a smaller daughter organism which eventually separates
  • this method occurs in hydra and yeast
36
Q

what is fragmentation? (2)

A
  • new organisms grow from separated fragment of parent organism
  • method is common to starfish and species of annelid worms
37
Q

what is parthenogenesis? (2)

A
  • embryos are formed from unfertilised ova (via production of a diploid egg by female)
  • this method of cloning occurs in certain species of insect, fish amphibians and reptiles
38
Q

how do plants have the capacity for vegetative propagation?

A

because adult plants possess meristematic tissue capable of cellular differentiation (totipotent)

39
Q

what are the 3 ways that humans are capable fo creating genetic clones through natural means?

A
  • identical twins (monozygotic) created when a fertilised egg (zygote) splits into 2 identical cells, each forming embryo
  • non-identical twins (dizygotic) are created when an unfertilised egg splits into 2 cdlls and each is fertilsied by different sperm
  • identical twins will be clones of one another, while non-identical twins will share 50% of same DNA
40
Q

how do plants regrow into new independent clones via vegetative propagation? (3)

A
  • all plants possess nodes where a leaf, branch or aerial root may grow - the region between nodes are called internodes
  • stem cuttings are typically placed in soil within the lower nodes covered and the upper nodes exposed
  • stem cutting is a common method employed to rapidly propagate plant species
41
Q

what are the variety of factors that will influence the successful rooting of a stem cutting?

A
  • cutting position (whether cutting occurs above or below node as well as relative proximity of the cut to the node)
  • length of cutting (including how many nodes remain on the cutting)
  • the use and concentration of growth hormone
  • temperature conditions (most cuttings grow optimally at temperatures common to spring and summer)
  • availability of water 9either in the form of ground water or humidity)
  • other environmental conditions (including pH of solid and light exposure)

Biology SL (38 decks)

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